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Öğe Frequency and voltage dependence of dielectric properties and electric modulus in Au/PVC + TCNQ/p-Si structure at room temperature(Elsevier, 2014) Kaya, A.; Vural, O.; Tecimer, H.; Demirezen, S.; Altindal, S.Au/PVC + TCNQ/p-Si structure was fabricated and real and imaginary parts of the dielectric constant (epsilon', epsilon ''), loss tangent (tan delta), and the real and imaginary parts of the electric modulus (M', M '') and ac conductivity (sigma(ac)) of this structure have been investigated in wide frequency a range of 1 kHz-5 MHz at room temperature. All of these parameters were found strong function of frequency and voltage especially in the inversion and depletion regions at low frequencies due to interfacial polarization and charges at interface states (N-ss). The decrease in epsilon' and epsilon '' with increasing frequency indicated that the interfacial dipoles have less time to orient themselves in the direction of the alternate field. While the value of M' increase with increasing frequency and reach a maximum, M '' shows a peak and the peak position shifts to higher frequency with increasing applied voltage. The ln(sigma(ac)) vs ln(omega) plot of the structure for 0.5 V has three linear regions (I, II and III) with different slopes which correspond to low, intermediate and high frequency ranges, respectively. Such behavior of ln(sigma(ac)) vs ln(omega) plot indicated that there are three different conduction mechanisms in the Au/PVC + TCNQ/p-Si structure at room temperature. (C) 2013 Elsevier B. V. All rights reserved.Öğe Frequency and voltage dependent profile of dielectric properties, electric modulus and ac electrical conductivity in the PrBaCoO nanofiber capacitors(Elsevier Science Bv, 2016) Demirezen, S.; Kaya, A.; Yeriskin, S. A.; Balbasi, M.; Uslu, I.In this study, praseodymium barium cobalt oxide nanofiber interfacial layer was sandwiched between Au and n-Si. Frequency and voltage dependence of epsilon', epsilon', tan delta, electric modulus (M' and M '') and sigma(ac) of PrBaCoO nanofiber capacitor have been investigated by using impedance spectroscopy method. The obtained experimental results show that the values of epsilon', epsilon', tand, M', M '' and sigma(ac) of the PrBaCoO nanofiber capacitor are strongly dependent on frequency of applied bias voltage. The values of epsilon', epsilon '' and tand show a steep decrease with increasing frequency for each forward bias voltage, whereas the values of sigma(ac) and the electric modulus increase with increasing frequency. The high dispersion in epsilon' and epsilon '' values at low frequencies may be attributed to the Maxwell-Wagner and space charge polarization. The high values of epsilon' may be due to the interfacial effects within the material, PrBaCoO nanofibers interfacial layer and electron effect. The values of M ' and M '' reach a maximum constant value corresponding to M-infinity approximate to 1/epsilon(infinity) due to the relaxation process at high frequencies, but both the values of M ' and M '' approach almost to zero at low frequencies. The changes in the dielectric and electrical properties with frequency can be also attributed to the existence of N-ss and R-s of the capacitors. As a result, the change in the epsilon', epsilon '', tan delta, M', M '' and ac electric conductivity (sigma(ac)) is a result of restructuring and reordering of charges at the PrBaCoO/n-Si interface under an external electric field or voltage and interface polarization. (C) 2016 The Authors. Published by Elsevier B.V.Öğe Temperature and Voltage Effect on Barrier Height and Ideality Factor in Au/PVC plus TCNQ/p-Si Structures(Wiley-Hindawi, 2014) Kaya, A.; Demirezen, S.; Tecimer, H.; Altindal, S.The forward bias current conduction mechanisms of Au/PVC + TCNQ/p-Si structures have been investigated in a wide temperature range of 120-420K for various applied bias voltage. The analysis of the main electrical parameters such as zero-bias barrier height (BH) (phi(Bo)), ideality factor (n), and interface states (N-ss) was found strongly dependent on temperature and voltage. The obtained results show that, while phi(Bo) increases, n decreases with increasing temperature. The plot of phi(app) versus q/2kT was drawn to show a Gaussian distribution (GD) of the BHs, and this plot shows two distinct linear regions. The phi(Bo) and standard deviation (sigma(s)) values were found from the slope and intercept of these plots for two regions as 1.16 eV and 0.161V for the first region and 0.71 eV and 0.093V for the second region, respectively. Such behavior is typical of a double GD (DGD) of the BHs due to the BH inhomogeneities at the metal-semiconductor interface. The slope and intercept of the modified (ln(I-0/T-2) - q(2)sigma(2)(0)/2k(2)T(2)) versus q/kT plot gives the and phi(Bo) and effective Richardson constant (A*) as 1.16 and 0.76 eV and 36.7 and 83.8 A/cm(2)K(2), respectively. The value of the A* (36.7 A/cm(2) K-2) is very close to the theoretical value of 32 A/cm(2) K-2 for p-Si. In addition, to interrupt the voltage-dependent activation energy, the ln(I-s/T-2) versus q/kT plot was drawn in the voltage range of 0-0.3V in 0.05V steps. All of experimental results confirmed that the BH or E-a values depend on the temperature as well as bias voltages.Öğe The effect of Mo-doped PVC plus TCNQ interfacial layer on the electrical properties of Au/PVC plus TCNQ/p-Si structures at room temperature(Elsevier Sci Ltd, 2015) Demirezen, S.; Kaya, A.; Vural, O.; Altindal, S.The effect of Mo-doped and undoped PVC+TCNQ interfacial layer on electrical characteristics of a Au/PVC+TCNQ/p-Si structure was investigated using current-voltage (I-V), capacitance-voltage (C-V) and conductance-voltage (G/omega-V) measurements at room temperature. The energy dependent interface states density (N-ss) was obtained from the forward bias I-V data by taking into account voltage dependent effective barrier height (Phi(e)) for two diodes,. i.e. with and without Mo doping. The voltage dependent resistance (R-i) of structures was also obtained using Ohm's law and the method of Nicollian and Brews for the diodes. In order to eliminate the effect of series resistance (R-s), C and G/omega at high frequency values were corrected. N-ss and R-s values were compared between the diodes and experimental results showed that N-ss and R-s values of the Mo-doped PVC+TCNQ structure are considerably lower than those of the undoped PVC+TCNQ structure. The other important parameters such as ideality factor (n), reverse saturation current (I-s), zero-bias barrier heights (Phi(B0)) and R-s were obtained from forward bias I-V data by using I-V, Cheung and Norde methods. Experimental results confirmed that the Mo-doped (PVC+TCNQ) layer considerably improved the performance of the Au/PVC+TCNQ/p-Si structure. (C) 2015 Elsevier Ltd. All rights reserved.Öğe The investigation of dielectric properties and ac conductivity of Au/GO-doped PrBaCoO nanoceramic/n-Si capacitors using impedance spectroscopy method(Elsevier Sci Ltd, 2016) Kaya, A.; Alialy, S.; Demirezen, S.; Balbasi, M.; Yeriskin, S. A.; Aytimur, A.Graphene oxide-doped praseodymium barium cobalt oxide (GO-doped PrBaCoO) nanoceramic was used an interfacial layer for the purpose of increasing the capacitance in Au/n-Si metal semiconductor (MS) structures. The frequency and voltage dependence of dielectric constant (epsilon'), dielectric loss (epsilon ''), loss tangent (tan delta), the real and imaginary parts of electric modulus (M' and M '') and ac electrical conductivity (sigma(ac)) of Au/GO-doped PrBaCoO nanoceramic/n-Si capacitors were investigated in detail by impedance spectroscopy method in the wide frequency range of 1 kHz to 1 MHz at room temperature. Experimental results showed that epsilon'-V plot has two distinct peaks that are located at about 0 and 2 V, respectively, at low frequencies, but the first peak disappears at high frequencies. While the value of M' increase with increasing frequency M '' shows a peak and the peak position shifts to higher frequency with increasing applied voltage. Such peak behavior can be attributed to the particular distribution of interface states located between Au and interfacial layer and to the interfacial polarization. It can be concluded that the interfacial polarization and the charges at interface can easily follow ac signal at low frequencies. In addition, the ln(sigma(ac)) vs ln(omega) plot of the capacitor for 3 V has two linear regions (I and II) with different slopes which correspond to low and high frequency ranges, respectively. Such behavior of ln(sigma(ac)) vs ln(omega) plot indicated that there are two different conduction mechanisms in the Au/GO-doped PrBaCoO nanoceramic/n-Si capacitor at room temperature. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
